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  #16  
Old 10-11-2008, 11:07 PM
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The car has a Swirl Pot in the tank. [ Some call it a flower pot]
Swirl Pots are used on many cars to make sure there is constant flow to the fuel pump at all conditions.
The screen is in the pot and just provides the last filtering of petro from the tank to the pump inlet [ where some have another screen].
If you have gravity flow from the pump inlet hose into container and it slows down, only to return flow after 30 secs , you have a partial blockage in the swirl pot and screen assem.
Most of this blockage will be in the manifold that feeds the screen and will be rust and dirt due it's location on the bottom of the tank. So, a screen cleaning is usually not the remedy, even if dirty.
There are several ways to clean the pot assembly... from blowing air into both the fuel inlet and return line, to actually accessing the pot from the gas sending unit hole and the manifold from the screen plug hole.

Don't use anything that can cause sparks..[ brass is good ..I use brazing rods for this type work..plastic is better.]
Don't use acid as you can melt the swirl Pot.

I am taking the liberty of posting from a JA post [ Tnx JA] on another group a picture to show you what you are dealing with, as a pic is much easier than for me to explain how these look. This is a view of a tank that has been cut open, so it is self explanitory.
The working principles of the system are that the fuel return line creates a vortex force into the pot and that aids the flow properties to the electric pump ..the pic shows this very well . Just imagine a small tank within your large tank , allowing for cornering, hills, etc when the large tank is low on fuel not effecting the fuel supply at the screen for the pump. The pot stays full , even when the main tank is very low.
BUT...If the tank is full beyond the OPEN top of the swirl pot , the pots purpose in mute b/c the screen is fed directly from the large tank... but crap in that lower mainfold where the screen sits will still be effected b/c that is still fuel pump hose feed.
When all is working, one should have a steady gravity flow from the pump inlet hose into a container if the tank fuel level is over the top of the swirl pot.
The return line is the flow factor when the tanks level is below the pots open top, where the return pressure adds force to the swirl and fuel is pulled into the pot via another small hole just below the return line attachment at the pot [ see pix]..this is a venturi effect princible and that hole is notorious for blockage, again, b/c of it's low location in the tank. I clean them w/brazing rod with a right angle bend and access it thru the gas gauge senser unit hole.
Careful !!!!! Gas is Dangerous !!!!

Here is an easy diagnostic rule of thumb for those interested on this type of fuel system:
If one does a fuel flow test at the main filter and the flow rate slows, check the fuel level gauge FIRST. If it is low , before going any further , put some more gas in the tank [ enough to be sure the level is OVER the top of the swirl pot.] If you then have proper flow rate, you don't have a blocked screen or manifold problem, you more likely have a problem with a dirty pot feed hole or clogged return line. This will show right up as a gas complaint when the fuel level goes below the pots top edge b/c the pot is now supplying the system from the return line and pots vortex hole.
Tricky diagnosis until you know how these work..then it is as simple as can be...the trick Techs use before going into all kinds of possibles is to add a 5 gal can of gas and retest flow rates. I have seen guys spend a fortune $$$$ buying pumps/filters/ and everthing in between for a simple plugged up swirl pot feed hole.....

Heres JA pix

http://www.sl113.org/forums/uploaded/ja17/200611475414_fuel%20tank%20with%20fp%20ill..JPG

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Last edited by Arthur Dalton; 10-11-2008 at 11:47 PM.
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  #17  
Old 10-11-2008, 11:46 PM
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Thanks for the detailed description Arthur.. i'm going to have a go at this tomorrow. The picture makes understanding how the system works much clearer.

Bryce
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  #18  
Old 10-12-2008, 04:02 AM
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Glad that photo was posted showing the swirl pot is plastic. You definately don't want to use acid!

Looking forward to hearing how your fix turns out!
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  #19  
Old 10-12-2008, 09:52 AM
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Hello Brice,

Yes, it is most important that you have a good clean fuel supply with proper pressure and volume. The fact that your main filter stays clean, and the car never completely stops driving (just will not idle) leads me to believe that you may want to check the warm running device (WRD) on your mechanical injection pump. This is mechanical warm up regulator which adjust the mixture during the engine warm up cycle. This is easy to check out. It is located on the back top of the injection pump and has two coolant hoses hooked to it. On the back side is a small round horizontal canister (actually an air filter) don't get it connfused with the electrical solenoids below. You can use a section of hose as a stethescope. When the engine is cold you will hear air rushing into the air canister. When the engine reaches operating temperature you should hear no rushing of air. These units will get stuck during long periods of inactivity (storage). If your WRD is stuck in cold position, the engine will be running much to rich to idle when warm, but may still drive. Maybe Arthur or myself can post some photos later.
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Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #20  
Old 10-12-2008, 10:18 PM
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Today I attempted to clean out the tank as best I could. I wasn't able to do a perfect job, but I did manage to remove quite a lot of gunk out of the swirl pot. Shame the sender isn't right above it, it would have made that job much easier!

Next step was to re-install the tank. That took most of the day... Quite a challenge with one person and the the car not being raised! (I really need to find a better place to work on the car). Eventually I got it in and the everything re-installed. Before I re-connected the return line I put it in a bottle and I was getting decent flow from the tank.. the colour of the petrol wasn't as good as I hoped since I had just filled the tank up with new petrol.

Anyway, I let the car idle for about 15 mins while I packed up all my tools and then took it for a drive for about 30 mins.. so far so good.. no stalling and seems to run ok. Not perfect, but ok - So probably would do it good to give it a nice run on the interstate and check that air filter that Joe mentioned too. (thanks for the tip!)

Anyway, I'll be taking it for more of a run next weekend, and thanks to everyone that replied to this thread.. the advice was invaluable!
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  #21  
Old 10-12-2008, 10:32 PM
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Very Good.

A trick I use whenever a good cleaning of a tank or screen has been done is after everything is put back together, but before running the engine, turn the key On and let the electric fuel pump circulate the complete fuel loop
[ tank>screen>pump>Main filter>return line>swirl pot >screen again.]
You can do that for a good 15/20 min. I even shake the ass end of the car to slosh the tank fuel around.

This get all the crap in the lines and parts to flush themselves via circulation and get collected in the screen and main filter housing again.
Then you remove the screen and filter housing and clean them again... it is just a loop filtering using the filters/screens you already have there and cleans up the system before running the Injection pump............................... it works !!!

No need to run the engine.....just the pump. It is also a good idea to disconnect the ign feed at ballast just to protect the ignition/coil circuit.
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Last edited by Arthur Dalton; 10-12-2008 at 10:56 PM.
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  #22  
Old 10-13-2008, 08:17 PM
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Hello,

There is also one additional fuel strainer/filter in the system to check. You need to remove the intake fitting of the electric fuel pump to check and clean it.
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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #23  
Old 10-13-2008, 08:58 PM
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Quote:
Originally Posted by ja17 View Post
Hello,

There is also one additional fuel strainer/filter in the system to check. You need to remove the intake fitting of the electric fuel pump to check and clean it.
Post #16.
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  #24  
Old 10-13-2008, 10:25 PM
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And post #9.
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  #25  
Old 10-13-2008, 10:51 PM
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Ah yes, it's good to carefully read all the threads when you come in late!

Well I guess I can add a bit of advice while I am at it; the fitting is difficult to remove when the electric fuel pump is in the car. However I have found it quite easy to remove while still on the car by using an air impact gun. Do not use and electric impact gun since sparks and gasoline are not a good combination. Always re-install by hand to prevent damage by over-tightening.
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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #26  
Old 10-13-2008, 10:53 PM
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1966 250SE Coupe Owner
 
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Yes. I remember that nut being a real tough one and I'm guessing that I probably did remove the pump and blast it off with a 1/2" drive air impact gun.
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  #27  
Old 10-18-2008, 11:16 AM
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Thanks for teh suggestion of the other screen in the fuel pump. I wanted to clean this, but I wasn't able to remove it. I did use a flashlight to look in there, and it seemed to be pretty clean from what i could see.

In any case, i've taken the car for two 35 mile drives since the weekend and its performed reasonably well. Even had it up to 80mph which would not have been possible before.

I do need to buy a new cork o-ring for the fuel sender as that one is toast and i'm leaking a bit from there. Next jobs are check all the belts and eliminate the belt squeal I get from the car, then start looking at the brakes (brake booster seems to have a leak in it, as i hear it hissing when I press the pedal and I need a lot of pressure to stop the car)
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  #28  
Old 10-19-2008, 01:06 AM
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1966 250SE Coupe Owner
 
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Most hardware stores sell cork gasket material by the sheet. Cheap, and easy to cut with scissors and make your own

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